Conventional rinse-added fabric softening compositions contain fabric softening agents which are substantially water-insoluble cationic materials usually having two long alkyl chains. Typical of such materials are distearyl dimethyl ammonium chloride and imidazolinium compounds substituted with two stearyl groups. These materials are normally prepared in the form of an aqueous dispersion or emulsion, and it is generally not possible to prepare such aqueous dispersions with more than about 6% of cationic material without taking special precautions to ensure acceptable viscosity and stability characteristics. Indeed, with cationic levels in excess of about 8% the problems of physical instability and high viscosity become, in the case of conventional fabric softening products, almost intractable. The formulation of fabric softener compositions with low levels of the active softener ingredients adds substantially to distribution and packaging costs.
In addition to shipping and packaging economy, another advantage of a more concentrated fabric softening composition is that it permits the consumer to exercise choice in the type of performance desired, in that the concentrated product can either be used as such or can be diluted to a conventional concentration before use. This opens up the possibility of supplying the concentrated fabric softening composition in a more economically packaged form intended for making up by the consumer into a conventional bottle.
The problem of preparing fabric softening compositions in concentrated form suitable for consumer use has already been addressed in the art, but the various solutions proposed have not been entirely satisfactory. U.S. Pat. No. 3,681,241, Rudy, issued Aug. 1, 1972, utilizes a combination of quaternary ammonium softener, saturated imidazolinium softener, unsaturated imidazolinium softener and ionizable salts to formulate concentrated softeners, but the maximum concentration achieved in that patent is only 13%. The use of certain special processing techniques for reducing viscosity has also been suggested (for example, in U.S. Pat. No. 3,954,634, Monson, issued May 4, 1976) but again this does not provide a complete and satisfactory solution, and it is not an easy matter to adopt this type of process on a commercial scale.
In U.S. Pat. No. 4,155,855, Goffinet et al., issued May 22, 1979, concentrated fabric softeners are disclosed which comprise three active softening ingredients, one of which is a highly soluble cationic fabric substantive agent. While such compositions do allow a high concentration of active ingredient, their overall softening performance is less cost effective then is the case with compositions containing predominantly a water-insoluble cationic softener. In U.S. Pat. No. 4,149,978, Goffinet, issued Apr. 17, 1979, mixtures of cationic softener and paraffinic materials are proposed in a certain ratio which can allow the preparation of concentrated softening compositions when relatively high proportions of paraffinic materials are employed. Paraffins are not essential components of the compositions of the present invention and are preferably absent therefrom. Dutch Patent Application No. 6706178 relates to viscosity control in fabric softening compositions with up to 12% of cationic softener, and suggests the use of low molecular weight hydrocarbons for this purpose. British Pat. No. 1,538,094, Hoechst, published Jan. 17. 1979, discloses a complex softener/disinfectant composition in which a long-chain fatty alcohol used at a relatively low ratio of cationic softener to alcohol is suggested as a solubilization aid. European Patent Application 0013780, published Aug. 6, 1980, discloses concentrated aqueous fabric softener compositions comprising a cationic softener and a viscosity control agent selected from the group consisting of hydrocarbons, fatty acids, fatty acid esters and fatty alcohols. European Patent Application 0018039, published Oct. 29, 1980, discloses concentrated aqueous fabric softening compositions comprising an insoluble cationic softener, a water-soluble nonionic or cationic surfactant and a hydrophobic adjunct selected from C.sub.12 to C.sub.20 paraffins and esters of C.sub.12 to C.sub.24 fatty acids and C.sub.1 to C.sub.8 fatty alcohols. Water-insoluble fatty nonionic materials are not essential to the compositions herein and are preferably absent therefrom.
The object of the present invention is to provide highly concentrated aqueous fabric softening compositions, based on cationic softener systems, which do not require substantial quantities of materials other than the cationic softeners to ensure physical stability and acceptable viscosity.